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Folded cascode operational amplifier

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Vivek_2017

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Hi guys,
I am trying to design a folded cascode operational amplifier with pmos input and a dc gain ≧70 dB in UMC 180 nm. All the transistor are working in saturation, but, I am getting gain -61 dB.
Can anyone please suggest the problem with this and how I can correct it.

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EdaBoardPhase&Gain.png
 

I suggest checking
1- if the transistors have sufficient overdrive voltage or not?
2- if the resistors of the common-mode feedback are large enough?
3- if the applied input voltage is differential or not?
 

Thanks for reply.
Resistor for common mode feedback are 10 Mohm, while there is drain to source potential of each and every transistor is 1.5 to 2 times that of VDS(saturation) and input is sinusoidal 100 mV (p-p) and differential in nature too.
 

I'd try and control CM voltage not at the cascode transistors' gates (4), but at the vdd side (1). Perhaps a too low-impedance (R1 || R2) CMFB control at node (4) might ruin your gain? To check this, you could try & rise the source impedance to node (4) first.
 
I'd suggest to feed the CM volatage to M10 (V5). You can divide the M5 to two transistor as it makes easier to control gain and CM-feedback.
 
Double check all the transistors in saturation region. You can do a plot with node voltage turning on.
 

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